I miss when you could write a URL like this in a browser, and it would render it:
about:Hello World
I made something similar at title.deno.dev, which you can use like this:
https://title.deno.dev/This is a title
It shows a page with the title you give it, and the title set in any bookmark or tab you save from it.
You can also add extra text to the page, which will be shown below the heading, but not be in the bookmark/tab title: